1. Field of the Invention
This invention relates generally to solid-state circuit interrupters and more specifically, to such circuit interrupters as are utilized in molded case and metal clad type circuit interrupters and as are capable of acting on a number of complex electrical parameters in order to protect the electrical conducting system and devices connected thereto. This invention further relates to such circuit interrupters that allow for system user interaction so that the number of electrical parameters can be easily and readily understood and responded to.
2. Description of the Prior Art
The solid-state circuit interrupter is being employed today for significantly more complex commercial and industrial applications than was the original circuit interrupter first introduced as a resettable replacement for a common fusing element. Additionally, with the recent explosion in the use and performance attributes of the microprocessor arts along with the coincident increasing cost advantage for such devices, the application of microprocessor teachings to the circuit interrupter field has brought a commensurate demand for more complex analysis, greater performance features, and easier interaction with the solid-state circuit interrupter while at the same time, maintaining or improving the cost factor for such circuit interrupters.
An existing microprocessor based solid-state circuit interrupter is disclosed in U.S. Pat. No. 4,331,997 issued to Engel and assigned to the same assignee as the present application. This device was able to apply microprocessor technology to existing circuit interrupters while maintaining the supervisory control over such factors as instantaneous protection, short delay protection, long delay protection and ground fault protection that were found on existing solid-state circuit interrupters such as those that utilized discrete or other integrated circuit electronic components. As examples of circuit interrupters utilizing discrete components, reference is now made to U.S. Pat. No. 3,590,326 issued to Watson on June 29, 1971 and U.S. Pat. No. 3,818,275 issued to Shimp on June 18, 1974. In addition, the microprocessor based circuit interrupter was able to incorporate display and input monitoring techniques that provided for more accurate and reliable interface and operation of the electrical distribution system on which the circuit interrupter was being utilized.
This processor based circuit interrupter also proved advantageous in energy management systems where it was necessary to configure the electrical distribution system to achieve maximum energy efficiency and a minimum circuit interruption to the system as a whole. It is well known in the field that in configuring an electrical distribution system, a main circuit interrupter which protects a line feeding a number of branch circuits each having a branch circuit interrupter disposed thereon, should have delay times assigned so that in the event of a fault in one of the branch circuits, the associated branch circuit interrupter would trip before the main circuit interrupter. In this manner, the entire electrical distribution system would not be interrupted by a fault condition in a branch circuit and, the device or devices which that branch circuit was feeding, would also be protected in a more timely manner. Still other zone interlocking conditions can be accommodated using similar design criteria as the above example.
The microprocessor based circuit interrupter also proved advantageous over existing circuit interrupters in the method of selecting and adjusting the tripping parameters. The electrical distribution system design was greatly simplified since it was no longer required that a trial-and-error approach to field timing the tripping parameters be performed.
This microprocessor based circuit interrupter though effective and certainly an advance over the then existing circuit interrupters, did have certain limitations that the present application addresses and overcomes. For instance, it would have been a great advantage to have a communication link tied to the microprocessor based circuit interrupter so that in working with an energy management system the circuit interrupter could be instructed from a remote location to perform various supervisory tasks such as, for example, a load shedding operation.
Another instance of a limitation of the referenced microprocessor based circuit interrupter is that the display arrangement provides for a time-multiplexed readout of the system operating characteristics; that is, a specific characteristic was displayed on one of two numeric displays while at the same time, a corresponding LED located adjacent to the numeric displays was illuminated to indicate the parameter being displayed. This numeric value and LED would remain on for a specific time duration, typically 3 to 4 seconds and then the next value and LED indicator would flash on for a corresponding amount of time. The coordination of the displayed numeric value to the LED for each of the two separate numeric displays in such a short time required a high level of familiarity on the part of the system operator.
Additionally, not only does this known method of display require coordination of the displayed value to the identifying LED, but then, in order to relate the significance of this value to the operating characteristics and tripping parameters associated with the circuit interrupter, the mental step of coordinating the display with a type of protection represented in a trip curve, must be performed. Furthermore, an instruction manual, generally provided as reference material in conjunction with the solid state circuit interrupter would be utilized as an operating tool by the system operator having a limited degree of familiarity with this device so that, when this instruction manual was referenced during viewing of the display panel, key information could have been multiplexed without being observed by the system operator. Additionally, because of the use of the solid state circuit interrupter in international markets, it becomes necessary to provide the instruction manuals in a wide variety of different languages.
Additionally, selecting the tripping parameters under which the solid state circuit interrupter is to operate, required further coordination between the displayed information and a group of selecting devices such as potentiometers or rotary switches. An example of a solid state circuit interrupter having a coordinated parameter selecting arrangement is found in U.S. Pat. No. 4,245,318 issued Jan. 13, 1981 to Eckart et al. This device utilized a graphic display and an array of control knobs to select the interrupter operating parameters for the one and adjacent circuit interrupters. However, this device requires a complex and expensive display arrangement and further, is effective primarily for setting up the parameters of the electrical distribution, but is of limited utility for monitoring continuing activities and operating characteristics at individual circuit interrupter locations.